In the use of communication links, a goal is to transport information from one physical location to another, sometimes over just a short distance between semiconductor devices. It is typically desirable that the transport of this information is reliable, is fast and consumes a minimal amount of resources. One of the most common information transfer mediums is the serial communications link, which may be based on a single wire circuit relative to ground or other common reference, multiple such circuits relative to ground or other common reference, or multiple circuits used in relation to each other.
In modern digital systems, it is desirable that digital information is processed in a reliable and efficient way. In this context, digital information is to be understood as information available in discrete, e.g., discontinuous, values. Bits, collection of bits, but also numbers from a finite set can be used to represent digital information.
The efficiency of digital communication systems can be expressed in terms of the time it takes to transfer certain amount of information (speed), the energy that is required to transmit the information reliably (power consumption) and, the number of wires or semiconductor device pins per bit that is required for communication (pin-efficiency). In many systems, several trade-offs exist between these parameters and, depending on the application, some of these parameters may be more important than others. In some chip-to-chip, or device-to-device communication systems, communication takes place over a plurality of wires to increase aggregate bandwidth. A single or pair of these wires may be referred to as a channel or link and multiple channels create a communication bus between the electronic components. At the physical circuitry level, in chip-to-chip communication systems, buses are typically made of electrical conductors in the package between chips and motherboards, on printed circuit boards (“PCBs”) boards or in cables and connectors between PCBs. In high frequency applications, microstrip or stripline PCB traces are often used.
Common methods for transmitting signals over bus wires include single-ended and differential signaling methods. In applications requiring high speed communications, those methods can be further optimized in terms of power consumption and pin-efficiency, especially in high-speed communications. Vector signaling methods based on Permutation Modulation Codes, Sparse Modulation Codes, or Superposition Signaling Codes, as taught by Cronie II, Cronie III, and Cronie IV, respectively, have been proposed to further optimize the trade-offs between power consumption, pin efficiency and noise robustness of chip-to-chip communication systems. In those vector signaling systems, the digital information is transformed into a different representation space in the form of a vector codeword, CW, that is chosen in order to optimize the power consumption, pin-efficiency and speed trade-offs based on the transmission channel properties and communication system design constraints. Herein, this process is referred to as “encoding”. At the receiver side, the received signals corresponding to the codeword CW are transformed back into the original digital information representation space. Herein, this process is referred to as “decoding”.
Conventional approaches to decoding are inefficient, ineffective and/or have undesirable side effects or other drawbacks with respect to at least one significant use case. For example, some conventional approaches are not amenable to optimization over a wide range of performance and complexity constraints. In particular, some conventional approaches require analog-to-digital converter circuitry that is problematic for high-speed and/or low power applications.
Embodiments of the invention are directed toward solving these and other problems individually and collectively.